6-48
The processor board has nine register tests. These are organized from the System jlP outward for
increasing confidence. One should always check multiple failures from top to bottom, investigating
each in turn.
Testing Method:
System jlP Register Tests-A12 Circuit Board:2100
PROCESSOR
If all bit patterns of a test fail, check for a defective chip select, a defective IC in the chip-select path,
or possibly the part under test is defective. If at least one bit pattern passes, use the "which bit
changed" method of isolating which bit(s) have the problem.
The register tests are organized by Circuit board. Where possible, a set of four bit patterns have been
used. The register tests have the capability of testing for stuck bits (both high and low) for each data
line as well as testing each data line for interconnecting shorts to other data lines.
All register names have the convention of assuming the name given to the schematic-designated chip-
select line for that register (i.e., MISC is the name of the chip select on the time base/display board to
registers U532 and U540).
From this level, all register tests are selected in turn. Individual tests may be executed by selecting test
numbers 2100 through 2600. If marked FAIL in the main Extended Diagnostics menu, move the cursor
to the 2000 level test and rerun to find next lower failure level in the Registers tests.
Table 6-6 (cont)
1100
ROMl
Base page ROM, A12U670.
1200
ROMO.O-O
Page 0, lower half of A12U680.
1300
ROMO.l-l
Page 1, lower half of A12U682.
1400
ROMO.2-2 Page 2, lower half of A12U690.
1500
ROMO.3-3
Page 3, lower half of A12U692.
1600
ROMO.0-4 Page 4, upper half of A12U680.
1700
ROMO.1-5 Page 5, upper half of A12U682.
1800
ROMO.2-6 Page 6, upper half of A12U690.
1900
ROMO.3-7 Page 7, upper half of A12U692.
2000
Registers Testing:
REG
Testing Method:
Maintenance-2430 Service
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